The switching-off of unrequired circuit blocks of a semiconductor circuit is an established process for drastically reducing leakage current losses in parts of the circuit which are temporarily unrequired. This process is extremely important, specifically in circuits which are critical with respect to power consumption such as, for example, in baseband circuits, in order to achieve a long standby time. For this purpose, a connection between a local ground of the circuit part to be switched off and the ground of the semiconductor circuit is nowadays usually interrupted using a single switch, such as a large negative metal-oxide semiconductor field effect transistor (NMOSFET) which has a low leakage current and is controlled via a central voltage supply signal. Similar solutions are also possible using a positive metal-oxide semiconductor field effect transistor (PMOSFET) and VDD switching. After switching-off, the inner capacitors of the switched-off circuit blocks are charged to VDD. After switching-on again, these capacitors have to be discharged again. During the re-switching-on procedure, uncontrolled switching processes (e.g., glitches, spikes) may occur, which cause, in addition to the discharge current for the capacitors, an additional current on supply lines of the semiconductor circuit. High current peaks should therefore be accommodated for shortly after switching on a circuit block again.
These current peaks, together with the inductors and the resistors of the supply voltage network of the semiconductor circuit, provide an excessive rise and/or fall in the supply voltage (resistive-inductive-capacitive (RLC) oscillator) and also disturb adjacent logic circuits which have not been switched off. However, the switching-off of the voltage supply of a voltage domain can also lead to high voltage peaks, as sudden changes which occur to a current during switching-off lead to voltage peaks, given correspondingly large inductances and low resistive attenuation. It is therefore desirable to monitor and minimize the current and voltage peaks during the switching-on and off of temporarily switched-off circuit blocks.
For these and other reasons, there is a need for the present invention.